A bit of idle banter between brothers-in-law on Christmas Day has turned into a $NZ2 million campaign ($1.88 million) to buy a privately owned New Zealand beach in one of the country's national parks and donate it to future generations.

Key points:

25,000 people donate $NZ1.6 million to help buy the private beach

7-hectare beach accessible by land, sea or foot, no road access

Plans to turn the beach over to NZ national parks authority

Wellington businessman owner to make decision on sale next week

When Duane Major and his brother-in-law Adam Gard'ner saw the Awaroa Bay beach for sale, they decided to set up a fundraising campaign to try to buy the beach, which is part of a private enclave inside Abel Tasman National Park at the top of the South Island.

Mr Major, who has visited the beach many times with young people in his role as a youth worker, was worried the property's access rights would allow a future owner to deny the public entry to the beach.

"It would be just nice to know it's ours and that slice of our identity that's wrapped up in our beautiful places is kept secure forever," he said.

The Government agency managing New Zealand's national parks, the Department of Conservation, did consider buying the land — it has bought other properties in Abel Tasman National Park — but decided against the purchase as it could not justify the price tag.

So Mr Major and Mr Gard'ner set about trying to raise the money and their idea has caught the public's imagination.

"We always had a belief in New Zealand spirit and the values we share around this. The first few days were very, very low and we thought we might be alone, but then: boom — it's really taken off since then," Mr Major said.

Three modest structures are on the property — one is a single room with basic kitchen facilities, the other an old fishing boat that has been spruced up and a woolshed that is part sleeping quarters and part storage.

There is no power, the water is stored in a couple of large tanks and the toilet system is, shall we say, rudimentary.

There are cleared tracks through the bush and the property is a moveable feast — its sand spit, locals say, has disappeared and reappeared over the years.

It last changed hands for $NZ1.9 million ($1.78 million) in 2008.

Political support for national park plan

Mr Major is hoping the campaign will reach its goal by the end of this week to allow him and his helpers to pull together a winning tender.

"We really hope that we can pledge early and strong to enable our tender process to be as robust and successful as possible," he said.

Such is the public enthusiasm, political parties have weighed in.

Conservation Minister Maggie Barry said she wants her department to talk to the fundraisers about making the beach part of the national park — if they win the tender.

Labour Party leader Andrew Little said the John Key Government should support the campaign and stump up any shortfall in the purchase price.

One wealthy New Zealander has already offered to meet any gap but philanthropist and economist Gareth Morgan struck a sour note by offering the money only if his family got exclusive use of part of the property.

That did not go down well with those who had already donated and Mr Major and Mr Gard'ner politely declined his offer.

Mr Major visited Awaroa Bay beach again last weekend.

"As soon as I got there on Saturday, I just ran straight in. It was just so gorgeous. I just thought 'welcome home'," he said.

The owner, low-profile Wellington businessman Michael Spackman, has five working days from next Tuesday, when the tender closes, to consider the offers and then make his decision public.